Evaluación de la contribución de la Antártida al nivel del mar desde el Último Periodo Glacial hasta el futuro

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, leída el 18/12/2020Sea-level rise is one of the biggest threats to modern humankind. The AntarcticIce Sheet (AIS) plays an important role in future projection, as it is the largest ice sheet on Earth, and hence the potential major contributor. However, as putin the Intergovernmental Panel on Climate Change (IPCC) fth report, the AISis also the largest source of uncertainty to sea-level rise. Part of this uncertainty arises due to uncertain future projections. Another source relies on the underlying mechanisms that drive the evolution of large continental ice sheets. Basal frictionas well as ice-ocean interactions are probably one of the most important, and yet unknown, building blocks in de ning the evolution of the AIS. This occurs because basal and sub-shelf processes are compounded into complex systems which are highly unconstrained. Through satellite observations it is possible to infer properties of these features but it does not give information about how it evolved in the past or the future. A way to gain insight into sub-shelf melting and basal friction, as well as future projections, is through paleo-modeling studies. Paleo-modeling studies are essential tools, as they allow not only analysis of the behaviour of ice sheets under past climatologies, but also to investigate the role of dierent features, such as ice dynamics, and compare with proxy data...Una de las consecuencias del aumento de temperaturas por emisiones antropogénicas es la subida del nivel del mar causada por el deshielo. La Antártida juega un papel importante en la predicción de estimaciones de aumento del nivel del mar ya que es el mayor manto de hielo de la Tierra. Sin embargo, según el quinto informe del Panel Intergubernamental de expertos del Cambio Climático, la Antártida es también la mayor fuente de incertidumbre a este respecto. Esta incertidumbre esta asociada por una parte al aumento de las temperaturas atmosféricas y oceánicas en los próximos años y por otra parte al hecho de que los modelos de mantos glaciares no resuelven todos los mecanismos subyacentes con precisión. En particular, la fricción que ejerce el lecho rocoso sobre el glaciar, así como las interacciones hielo-océano constituyen dos componentes básicos que no están representados correctamente en modelos de hielo. A través de observaciones de satélite es posible inferir propiedades en la base de mantos glaciares, sin embargo, no permiten obtener información sobre la evolución pasada o futura. Una forma de profundizar las interacciones hielo-océano y fricción basal es a través de estudios de paleo modelización. Estos estudios constituyen herramientas esenciales ya que no solo permiten analizar la evolución de los mantos de hielos a otros climas, sino también la sensibilidad de diferentes parámetros y comparar con datos observacionales...Fac. de Ciencias FísicasTRUEunpu

Chromium content in different kinds of spanish infant formuale and estimation of dietary intake by infants fed on reconstituted powder formulae

The essentiality of chromium in humans is well documented. Trivalent chromium, main chemistry form found in foods, is essential for maintaining normal glucose metabolism. Because of analytical difficulties, several literature reports of chromium content of foods, especially for the lower levels, show large variability and they should be interpreted with caution for a valid interpretation of reliable results. A Zeeman background correction transversely-heated graphite furnace atomic absorption spectrometry was used to determine the chromium content of 104 different infant formulae (cow’s milk and soy protein based) marked in Spain following an acid attack sample preparation procedure in a closed, pressurized and microwave digestion unit. Mean and range chromium values, regarding types and main protein-based infant formulae are presented. Additionally, the influence of the type of container used, the impact of industrial process from different manufacturers and the physical state (powder and liquid formulae) on chromium levels is also discussed. In general, the infant formulae contain a higher chromium concentration than that found in human milk (reference range: 0.20 – 8.18 g l-1), particularly in case of hypoallergenic (18.16 ± 7.89 g l-1), lactose-free (11.37 ± 3.07 g l-1), preterm (11.48 ± 3.15 g l-1) and soya (10.43 ± 4.05 g l-1) formulae. The maximum theoretical estimated intake of infant fed on studied formulae was lower than the upper limit safety for trivalent chromium of 1 mg kg-1 (14 g Kg-1 b.w. day-1) recommended by the experts of Council for Responsible Nutrition (CRN ULS, 2004), amounting to about 10 %, 15-18 % and 26 % for standard (adapted and follow-up) and toddler; soya, lactose-free and preterm; and hypoallergenic formulae, respectively. Therefore, manufacturers are called for continued effort to routinely monitor chromium levels, mainly for specialised and preterm formulae, and at the same time, might consider the inclusion of labelling value for chromium at least in these complex formulations

Surveillance of aflatoxin content in dairy cow feedstuff from Navarra (Spain)

Aflatoxins (B1, B2, G1 and G2) are produced by the fungi Aspergillus (A. flavus and A. parasiticus) in substrates used in cattle feed manufacturing. Aflatoxin M1 (AFM1) is a major metabolite of Aflatoxin B1 (AFB1) which may be present in milk from animals that consume contaminated feed. Levels of aflatoxins in 78 dairy cow feedstuff samples from 40 farms located in Navarra were determined by HPLC-FLD (High Performance Liquid Chromatography with fluorescence detection) and post-column derivatization. The influence of geographical location, season and type of feeding system on aflatoxin content was studied. The climatic profile of AFB1 pointed to spring as the season with the highest aflatoxin level (0.086 μg/kg), followed by winter and summer (0.075 and 0.030 μg/kg, respectively), and to a lesser degree, autumn (0.017 μg/kg). Moreover, wet and dry TMR (Total Mixed Ration) feeding systems (i.e. AFB1: 0.076 and 0.068 μg/kg; Aflatoxin G1 (AFG1): 0.050 and 0.011 μg/kg, respectively) showed a greater content of the analyzed aflatoxins in comparison with compound feed (i.e. AFB1: 0.039 μg/kg; AFG1: 0.007 μg/kg). The fact that the majority of the samples collected were based on compound feed shows that this type was preferred by most dairy farmers. The undetectable levels of aflatoxins in the organic homemade compound feedstuff are also worth mentioning. While none of the feedstuff samples contained amounts over those permitted under European legislation (5 μg/kg), the theoretical extrapolation of the carryover rate suggested in previously published experiments of AFB1 to AFM1 in secreted cow's milk predicts that only one of the feed samples studied had a positive aflatoxin level (53.4 ng/kg) higher than the legal limit for raw cow's milk

Optimization of a Slurry Dispersion Method for Minerals and Trace Elements Analysis in Infant Formulae by ICP OES and FAAS

Infant formula developed by manufacturers requires a rigorous control of composition, particularly those elements added routinely in an attempt to mimic the mineral composition of human milk. A total of 97 different types of powdered infant formulae (preterm, adapted starter, adapted follow-up, toddler, specialised and soy based formulae) commercially available in Spain were studied. It is noteworthy great differences in mineral (Ca, P, Mg) and trace element (Zn, Fe, Cu, Mn) contents found between analysed and listed in label information. The development of a fast, simple and direct slurry method for the determination of these essential micronutrients in infant formula by inductively coupled plasma optical emission spectrometry (ICP OES) and flame atomic absorption spectrometry (FAAS) was performed in order to help in quality control tasks. Infant formula samples were solubilised using different amounts of several different solvents. An addition of 250 L of a solution 10 % tetramethylammonium hydroxide and 25 % ammonium hydroxide were required for the accurate quantification of Ca and P, Mg, Zn, Fe, Cu and Mn, respectively. The standard reference material 1549 non-fat milk powder was solubilised to compare the validity of assayed methodology following slurry nebulisation and traditional microwave-assisted acid digestion method. Good agreement of the analytical results by both ICP OES and FAAS, with the certified values was obtained. Method performance parameters (accuracy, precision and methodological detection limits) were determined for studied elements to check the quality and usefulness of the optimised slurry method. The analytical procedure was applied successfully to the analysis of a representative group of infant formulae. Levels of analysed elements were graphically represented, showing an acceptable comparability between slurry and acid-mineralisation method set by linear correlation coefficients and slopes close to the unit. The described simple and slurry method is appropriate, as an attractive alternative, for routine control analysis of added essential elements in infant formulae regardless of predominant protein type used in manufacture

Estimation of dietary intake and content of lead and cadmium in infant cereals marketed in Spain

Lead and cadmium have become highly toxic metallic elements. There is an obvious 5 toxicological impact of these elements on infants since their intestinal absorption is 6 significantly higher than in adults, thus it is desirable to quantify lead and cadmium levels in 7 commonly consumed infant foods. Zeeman background correction, transversely heated 8 graphite furnace atomic absorption spectrometry, was used to determine both the lead and 9 cadmium content of 91 Spanish infant cereals. Cereals were assessed in terms of different 10 types, cereal predominant in formulation and whether it was obtained organically or 11 conventionally. Preliminary analysis revealed a noticeably higher content of lead and 12 cadmium (median, Q1-Q3) in organic cereals (n = 17, Pb: 26.07; 21.36-51.63; Cd: 18.52; 16.56-28.50 μg kg-1 13 ) in relation to conventional ones (n =74, Pb: 10.78; 6.43-19.33; Cd: 7.12; 4.40-11.77 μg kg-1 14 ). Three formulations exceeded European lead maximum levels. Added 15 ingredients (milk, cocoa, fruit and honey) to the cereal base provide lead enrichment. For 16 cadmium, this pattern was observed by cereal based on cocoa, but also the raw materials 17 contributed with a dilution phenomenon, decreasing the final cadmium concentration in infant 18 cereal. Apart from several organically produced cereals, lead content showed a narrow 19 variation, where gluten-free cereals provide lower cadmium content than formulations 20 containing gluten. Dietary intakes of both elements were assessed in comparison with the 21 reference intake values proposed by the EFSA Panel on Contaminants in the Food Chain. 22 Organic infant cereals based on honey and cocoa supplied the highest risk intakes of lead and 23 cadmium, respectively. In accordance with the actual state of knowledge on lead and 24 cadmium toxicity and attending to the upper limits calculated from risk intake values set by 25 EFSA, it seems prudent to call for a revision of both heavy metals content regulated by EC to set a maximum guideline values for infant cereal at 55 and 45 μg kg-1 26 , respectively

Survey of total mercury and arsenic content in infant cereals marketed in Spain and estimated dietary intake.

Due to the fact that infants and children are especially sensitive to mercury and arsenic 7 exposure, predominantly through diet, a strict control of the most widely consumed 8 infant foods, especially infant cereals, is of paramount importance. Levels of both total 9 mercury and arsenic in 91 different infant cereals from ten different manufacturers in 10 Spain were determined by flow injection adapted to cold vapor and hydride generation 11 atomic absorption spectrometry, respectively. Cereals were assessed in terms of the 12 different types, the predominating cereal in the formulation, the added ingredients, and 13 whether the cereal was organically or conventionally obtained. In general, the content of 14 toxic elements (median (Q1;Q3)) found in infant cereals based on conventionally obtained raw materials (n=74, Hg: 2.11 (0.42;4.58), As: 21.0 (9.4;50.9) μg·Kg-1 15 ) was 16 lower than in cereals produced by organic methods (n= 17, Hg: 5.48 (4.54;7.64), As: 96.3 (87.5;152.3) μg·Kg-1 17 ). Mercury content in infant cereals shows the higher values in 18 those formulations with ingredients susceptible to particulate contamination such as 19 gluten-free or cacao-based cereals. The highest arsenic content appears in the rice-based 20 cereals. The mercury and the inorganic arsenic dietary intakes for infants fed on the 21 infant cereals studied were assessed, taking into account the different stages of growth. 22 Organic infant cereals based on cocoa showed the highest risk intakes of mercury, very 23 close to exceeding the intake reference. Just the opposite, 95% of the organically 24 produced infant cereals and 70% of the conventional gluten-free infant cereals showed 25 an inadmissible risk of arsenic intake. Thus, it seems prudent to call for continued 26 efforts in standardizing routine quality control and in reducing arsenic levels in infant 27 cereals; in addition it is essential that relevant legislation be established and regulated 28 by EC regarding these two toxic elements

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Chemometric analysis of minerals and trace elements in raw cow milk from the Community of Navarra

The concentrations of protein, fat, five minerals (Na, K, P, Ca and Mg) and nine trace elements (Fe, Zn, Cu, Mn, Se, Al, Cd, Cr and Pb) have been determined in 347 samples of raw cow milk from the community of Navarra, north Spain, using infrared analysis, atomic absorption spectrometry (flame and electrothermal atomisation) and inductively coupled plasma atomic emission spectroscopy. A preliminary chemometric study with the use of pattern recognition methods was carried out in order to characterise, classify and distinguish the different collected samples on the basis of their contents. Principal component analysis (PCA) has permitted the reduction of 16 variables to five principal components which interpret reasonably well the correlations of these studied variables. These variable associations may be attributed to intrinsic (lactogenesis) and other extrinsic factors, such as seasonal variation, animal feeding or geographical situation. Changes in these contents during different seasons were also assessed and consistently interpreted. Linear discriminant analysis (LDA) was used to explore cow milk samples, classifying according to season or geographical location, providing complementary information to PCA. This work shows that PCA and LDA are useful chemometric tools for the multivariate characterisation of raw cows’ milk

Lead levels in retail samples of spanish infant formulae and their contribution to dietary intake of infants

Lead concentrations in a total of 82 different types of infant formulae (cow’s milk and soy based) marked in Spain were analysed by acid-microwave decomposition and anodic stripping voltammetry. Dietary lead intake from infant formula and tap water used for powder formula reconstitution were estimated in comparison with the provisional tolerable weekly intake (PTWI). Additionally, the influence of physical state (powder and ready to use formulae), the type of container used and the impact of industrial process from different manufacturers on lead levels were evaluated. According to our results, lead exposure from drinking water was negligible with respect to formulae investigated; where soya formulae contributed the highest intake (58 – 73 % PTWI), non adapted starter and specialised formulae gave an moderate intake (31 – 42 and 26 – 37 % PTWI, respectively) and, finally, pre-term, adapted starter and follow up formulae provided the lowest lead intake (22 – 25, 22 – 26 and 16 – 22 % PTWI, respectively). Based on the current state of knowledge about lead toxicity, manufacturers are called to make an additional effort in order to keep a maximum lead level at 20 g l-1 for all infant formulae, although it is recommendable that these formulations supply the upper limit (5 g l-1) of “normal” human milk